New Deep-sea Species Discovered During Mining Test At 4,000 Meters

There is a high demand globally of critical metals, and many countries want to try extracting these sought-after metals from the seabed. An international study, which has discovered large numbers of new species at a depth of 4,000 meters, shows that such mining has less of a negative impact than expected. However, species diversity declined by a third in the tracks of the mining machine.

In a major research project, marine biologists from several countries have attempted to map life in one of the least explored places on Earth: the deep-sea floor of the Pacific Ocean.

The study, published in Nature Ecology and Evolution, would not have been possible without significant commercial and geopolitical interest in the area.

“Critical metals are needed for our green transition, and they are in short supply. Several of these metals are found in large quantities on the deep-sea floor, but until now, no one has shown how they can be extracted or what environmental impact this would have,” says marine biologist Thomas Dahlgren, that together with Helena Wiklund, also at the University of Gothenburg, have participated in the research project.

160 days at sea

The research is being conducted in accordance with the International Seabed Authority’s (ISA) guidelines for baseline studies and environmental impact assessments (see fact box).

Over a period of five years, researchers have inventoried the marine life on the seabed and tested the impact of mining in an area between Mexico and Hawaii, known as the Clarion-Clipperton Zone. The study shows that the number of animals decreased by 37 percent and species diversity declined by 32 percent in the tracks of the machine that extracted the metals.

“The research required 160 days at sea and five years of work. Our study will be important for the International Seabed Authority (ISA), which regulates mineral mining in international waters,” says Thomas Dahlgren.

The researcher identified a new solitaire coral attached to polymetallic nodules. It was named Deltocyathus zoemetallicus. Photo: Natural History Museum, London & Göteborgs universitet

788 species

The examined deep-sea floor is 4,000 meters below water surface, no sunlight reaches there, and this means that it is an extremely nutrient-poor environment where the sediment layer grows by one thousandth of a millimeter per year. A bottom sample from, for example, the North Sea can contain 20,000 animals. A corresponding sample from the deep-sea floor yields the same number of species but only 200 specimens.

The researchers have collected 4,350 animals larger than 0.3 mm that live in, and sometimes on, the sea floor. 788 species were identified. The animals found were mainly marine bristle worms, crustaceans, and mollusks such as snails and mussels.

But there is also a new solitaire coral, that are described in another study.

Species distribution unknown

“I have been working in the Clarion-Clipperton Zone for over 13 years, and this is by far the largest study that has been conducted. In Gothenburg, we led the identification of marine polychaete worms. Since most species have not been described previously, molecular (DNA) data was crucial in facilitating studies of biodiversity and ecology on the seabed, says Thomas Dahlgren.

During the inventory, the researchers observed that the seabed communities changed naturally over time, probably due to changes in the amount of food reaching the seabed. Exactly how widespread the different species are across the deep-sea floors of the Pacific Ocean is unknown.

A sea spider. This is a type of animal that is related to land spiders but does not belong to that group. They can grow to the size of a palm in the deep sea around Antarctica, but this particular species is only a few millimeters in size Photo: Natural History Museum, London & Göteborgs universitet

“It is now important to try to predict the risk of biodiversity loss as a result of mining. This requires us to investigate the biodiversity of the 30 percent of the Clarion-Clipperton Zone that has been protected. At present, we have virtually no idea what lives there,” says Adrian Glover, senior author from the Natural History Museum of London.

Impacts of an industrial deep-sea mining trial on macrofaunal biodiversity, Nature Ecology and Evolution (open access)

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